1. Field of the Invention
This invention generally relates to solid state DC power control. More particularly, this invention relates to a microprocessor based solid state DC power controller arrangement where a microprocessor provides a powering signal to a solid state switch to selectively couple a load to a power source.
2. Description of the Prior Art
A variety of ways have been used to couple loads to power sources. Depending upon the current levels involved and the environment in which the load must operate, the type of switching arrangement can vary widely.
In many instances, there is a need to minimize the size and weight of the control arrangement. Solid state power controllers have been used in aircraft applications, for example. Such controllers have typically been hybrid devices utilizing field effect transistors (FET) to perform the actual current switching. Typically, a switching power supply DC-DC converter is used to provide power for the FET control and monitoring circuitry. Optocouplers typically are used to send control signals to the FET. The load is monitoring typically is accomplished by using analog amplifiers and voltage-to-frequency or voltage-to-pulse width modulation conversion to communicate load current values to low voltage control logic through additional optocouplers. In some instances, analog circuitry directly performs the load current monitoring and a circuit breaker function in the event of an over current situation.
While such arrangements have performed adequately under many circumstances, those skilled in the art are always striving to make improvements. Lighter weight, less complicated circuitry and increased robustness and versatility are all desirable. This invention provides an improved, more economical, versatile and more robust arrangement compared to conventional approaches.
In general terms, this invention is a system for selectively coupling an electrically powered load with a power source.
A system designed according to this invention includes a solid state switch having a gate that is energized to switch the solid state switch into a state to conduct electrical current between the power source and the load. A controller output is coupled to the solid state switch gate to provide power to the gate. The controller selectively provides a powering signal to the solid state switch gate. The controller cyclically and repeatedly provides the powering signal a selected number of cycles within a selected time period to ensure that the switch is maintained in a closed, conducting state as needed.
A charge pump that increases the powering signal preferably is coupled between the controller output and the switch gate. The charge pump provides the ability to adequately energize the gate while only requiring a small powering signal from the controller.
In one example, during times when the controller is not providing the powering signal, the controller is performing other functions or operations. The amount of time during which the controller provides the powering signal depends upon, in part, performance characteristics of the chosen solid state switch and other circuit components.
One example includes a surge protection portion coupled between the solid state switch and the controller to prevent current flowing through the solid state switch from being received by the controller.
One example includes a current indicator that provides an indication of a current flowing through the solid state switch between the power source and the load. The controller preferably interprets information regarding the current and selectively turns off the switch in the event that the flowing current exceeds a selected threshold.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawing that accompanies the detailed description can be briefly described as follows.